Many heart failure patients also suffer from respiratory disorders. Respiratory disorders common in heart failure patients include apnea and hypopnea, which may cycle, as characteristic of Cheyne-Stokes respiration (CSR). Apnea and CSR burden the heart with transient episodes of hypoxia and surges in sympathetic tone, which can exacerbate heart failure. Thus, a need exists for therapies to break or terminate apnea or CSR. However, diagnosis of an abnormal respiratory pattern should occur prior to implementation of such therapies.
As described herein, various exemplary methods, devices, systems, etc., detect respiratory issues using an evoked response measure and an impedance measure. In various situations, the evoked response measure or the impedance measure may indicate whether heart failure has improved or worsened. In turn, such diagnosis or information may be used to adjust therapy delivered, for example, by an implantable stimulation device.